Polymer Emboli Complicating Transcatheter Aortic Valve Implantation: A Case Report

Evaluation of hydrophilic polymer embolization from endovascular sheath devices in an in vitro perfusion system

Objective

Case reports, tissue pathology, and autopsies have suggested that the hydrophilic polymer coating designed to improve endovascular deliverability and minimize vessel trauma can embolize and be associated with adverse outcomes such as ischemia, infarction, and death. This study sought to determine whether hydrophilic polymers shed off commercially available sheaths in a controlled in vitro environment, with the hypothesis that significant differences between coated and uncoated (control) sheaths would be found.

Methods

Six sheaths from each manufacturer, including Zenith Alpha abdominal endovascular stent grafts (Cook Medical), DrySeal sheaths (W.L. Gore & Associates), and Sentrant Introducer sheaths (Medtronic), were tested in an in vitro environment. Noncoated Check-Flo performer introducer sheaths (Cook Medical) were used as controls. Each test circuit ran for 150 minutes at an output of 3 L/min, the circuit was then drained and the fluid collected. Quantitative analysis included weighing the dried filter paper and using particle size light scattering to quantify the particle size and count. Attenuated total reflectance spectroscopy was also used.

Results

Each of the three coated sheaths had significantly greater shedding compared with the control sheaths. The Cook Zenith alpha sheath had significantly more residue weight (2.87 ± 0.52 mg/L) than the Gore DrySeal (1.07 ± 0.06 mg/L) and Medtronic Sentrant introducer (0.98 ± 0.14 mg/L) sheaths. The average particle size was not significantly different between the coated and uncoated (control) sheaths. Attenuated total reflectance spectroscopy identified sheath particulate in the Cook Zenith Alpha and Medtronic Sentrant samples.

Conclusions

Polymer embolization was present and significantly greater in all three commercially available hydrophilic sheaths compared with the control group. Further investigation is needed into the clinical significance of these findings.

Technical Aspects and Development of Transcatheter Aortic Valve Implantation

Aortic stenosis is the most common valve disease requiring surgery or percutaneous treatment. Since the first-in-man implantation in 2002 we have witnessed incredible progress in transcatheter aortic valve implantation (TAVI). In this article, we review the technical aspects of TAVI development with a look at the future. Durability, low thrombogenicity, good hydrodynamics, biocompatibility, low catheter profile, and deployment stability are the attributes of an ideal TAVI device. Two main design types exist-balloon-expandable and self-expanding prostheses. Balloon-expandable prostheses use a cobalt-chromium alloy frame providing high radial strength and radiopacity, while the self-expanding prostheses use a nickel-titanium (Nitinol) alloy frame, which expands to its original shape once unsheathed and heated to the body temperature. The valve is sewn onto the frame and consists of the porcine or bovine pericardium, which is specially treated to prevent calcinations and prolong durability. The lower part of the frame can be covered by polyethylene terephthalate fabric or a pericardial skirt, providing better sealing between the frame and aortic annulus. The main future challenges lie in achieving lower rates of paravalvular leaks and new pacemaker implantations following the procedure, lower delivery system profiles, more precise positioning, longer durability, and a good hemodynamic profile. Patient-specific design and the use of autologous tissue might solve these issues.